1. Field of the Invention
The present invention relates to a bending tube for endoscope which performs a bending motion according to an operation of an operation portion and an endoscope.
2. Description of the Related Art
Conventionally, an endoscope which causes an object image of an inside of a body cavity to be displayed on a screen of a display device or the like by inserting an elongated insertion portion into the body cavity has been widely used. In general, a bending portion is provided on a distal end side of the insertion portion of the endoscope of this kind, and the bending portion is configured, for example, so that it freely bends in two directions of up and down, two directions of right and left or four directions of the up, down, right and left associated with the object image displayed on the display device or the like.
Recently, a bending tube for which a super-elastic alloy material is used has been proposed as a bending tube constituting such a bending portion. For the bending tube of this kind, for example, it is possible to realize a simple configuration without using a joint piece, a rotation pin or the like and easily realize diameter reduction, by providing a plurality of slots on a cylindrical-shaped pipe material (a bending tube body) using laser machining or the like.
Therefore, it is expected to adopt a bending tube made of a super-elastic alloy for an endoscope for which diameter reduction is especially required, such as a pyeloscope. In such an endoscope, it is common to adopt a configuration in which the bending portion can bend only in the two directions of up and down or only in the two directions of right and left in order to realize diameter reduction of the insertion portion more effectively. In the endoscope capable of bending only in two directions, it becomes possible to cause a distal end portion to be oriented to an arbitrary direction in a body cavity by combining a bending operation of the bending portion and a rotation-around-axis operation of the insertion portion.
In this case, for example, Japanese Patent Application Laid-Open Publication No. 2012-528651 (Patent Literature 1) discloses a technique in which each groove (each slot) arranged in a predetermined area which includes a proximal end side of a tube (a bending tube) is machined into a three-dimensionally bent zigzag shape (a crank shape) to form a projecting portion (a tab) and a pocket in the groove, and torsion of the bending tube is prevented by engaging the projection portion and the pocket, as a technique for preferably transmitting rotation torque around an axis given to the bending tube.